Background Applications
The present application also incorporates herein by reference the entire disclosures of all of the following patent applications for background reference:                1) U.S. Provisional Application No. 60/891,349, filed Feb. 23, 2007, to K. Taniuchi, et al.;        2) U.S. Provisional Application No. 60/825,567, filed Sep. 13, 2006 to Y. A. Cheng, et al.;        3) U.S. application Ser. No. 11/567,134, filed Dec. 5, 2006, to Y. Oba, et al.;        4) U.S. application Ser. No. 11/563,000, filed Nov. 23, 2006, to Y. Oba, et al.;        5) U.S. application Ser. No. 11/558,922, filed Nov. 12, 2006, to Y. Oba, et al.;        6) U.S. application Ser. No. 11/460,616, filed Jul. 27, 2006, to Y. Oba, et al.;        7) U.S. application Ser. No. 11/279,856, filed Apr. 14, 2006, to A. Dutta, et al., entitled Framework Of Media-Independent Pre-Authentication Improvements:        8) Including Considerations For Failed Switching And Switchback;        9) U.S. application Ser. No. 11/308,175, filed Mar. 9, 2006, to Y. Oba, et al., Framework of Media Independent Pre-Authentication Support for PANA;        10) U.S. application Ser. No. 11/307,362, filed February 2006, to A. Dutta, et al., entitled A Framework of Media-Independent Pre-authentication.        
Background Discussion
Networks and Internet Protocol:
There are many types of computer networks, with the Internet having the most notoriety. The Internet is a worldwide network of computer networks. Today, the Internet is a public and self-sustaining network that is available to many millions of users. The Internet uses a set of communication protocols called TCP/IP (i.e., Transmission Control Protocol/Internet Protocol) to connect hosts. The Internet has a communications infrastructure known as the Internet backbone. Access to the Internet backbone is largely controlled by Internet Service Providers (ISPs) that resell access to corporations and individuals.
With respect to IP (Internet Protocol), this is a protocol by which data can be sent from one device (e.g., a phone, a PDA [Personal Digital Assistant], a computer, etc.) to another device on a network. There are a variety of versions of IP today, including, e.g., IPv4, IPv6, etc. Each host device on the network has at least one IP address that is its own unique identifier. IP is a connectionless protocol. The connection between end points during a communication is not continuous. When a user sends or receives data or messages, the data or messages are divided into components known as packets. Every packet is treated as an independent unit of data.
In order to standardize the transmission between points over the Internet or the like networks, an OSI (Open Systems Interconnection) model was established. The OSI model separates the communications processes between two points in a network into seven stacked layers, with each layer adding its own set of functions. Each device handles a message so that there is a downward flow through each layer at a sending end point and an upward flow through the layers at a receiving end point. The programming and/or hardware that provides the seven layers of function is typically a combination of device operating systems, application software, TCP/IP and/or other transport and network protocols, and other software and hardware.
Typically, the top four layers are used when a message passes from or to a user and the bottom three layers are used when a message passes through a device (e.g., an IP host device). An IP host is any device on the network that is capable of transmitting and receiving IP packets, such as a server, a router or a workstation. Messages destined for some other host are not passed up to the upper layers but are forwarded to the other host. The layers of the OSI model are listed below. Layer 7 (i.e., the application layer) is a layer at which, e.g., communication partners are identified, quality of service is identified, user authentication and privacy are considered, constraints on data syntax are identified, etc. Layer 6 (i.e., the presentation layer) is a layer that, e.g., converts incoming and outgoing data from one presentation format to another, etc. Layer 5 (i.e., the session layer) is a layer that, e.g., sets up, coordinates, and terminates conversations, exchanges and dialogs between the applications, etc. Layer-4 (i.e., the transport layer) is a layer that, e.g., manages end-to-end control and error-checking, etc. Layer-3 (i.e., the network layer) is a layer that, e.g., handles routing and forwarding, etc. Layer-2 (i.e., the data-link layer) is a layer that, e.g., provides synchronization for the physical level, does bit-stuffing and furnishes transmission protocol knowledge and management, etc. The Institute of Electrical and Electronics Engineers (IEEE) sub-divides the data-link layer into two further sub-layers, the MAC (Media Access Control) layer that controls the data transfer to and from the physical layer and the LLC (Logical Link Control) layer that interfaces with the network layer and interprets commands and performs error recovery. Layer 1 (i.e., the physical layer) is a layer that, e.g., conveys the bit stream through the network at the physical level. The IEEE sub-divides the physical layer into the PLCP (Physical Layer Convergence Procedure) sub-layer and the PMD (Physical Medium Dependent) sub-layer.
Wireless Networks:
Wireless networks can incorporate a variety of types of mobile devices, such as, e.g., cellular and wireless telephones, PCs (personal computers), laptop computers, wearable computers, cordless phones, pagers, headsets, printers, PDAs, etc. For example, mobile devices may include digital systems to secure fast wireless transmissions of voice and/or data. Typical mobile devices include some or all of the following components: a transceiver (i.e., a transmitter and a receiver, including, e.g., a single chip transceiver with an integrated transmitter, receiver and, if desired, other functions); an antenna; a processor; one or more audio transducers (for example, a speaker or a microphone as in devices for audio communications); electromagnetic data storage (such as, e.g., ROM, RAM, digital data storage, etc., such as in devices where data processing is provided); memory; flash memory; a full chip set or integrated circuit; interfaces (such as, e.g., USB, CODEC, UART, PCM, etc.); and/or the like.
Wireless LANs (WLANs) in which a mobile user can connect to a local area network (LAN) through a wireless connection may be employed for wireless communications. Wireless communications can include, e.g., communications that propagate via electromagnetic waves, such as light, infrared, radio, microwave. There are a variety of WLAN standards that currently exist, such as, e.g., Bluetooth, IEEE 802.11, and HomeRF.
By way of example, Bluetooth products may be used to provide links between mobile computers, mobile phones, portable handheld devices, personal digital assistants (PDAs), and other mobile devices and connectivity to the Internet. Bluetooth is a computing and telecommunications industry specification that details how mobile devices can easily interconnect with each other and with non-mobile devices using a short-range wireless connection. Bluetooth creates a digital wireless protocol to address end-user problems arising from the proliferation of various mobile devices that need to keep data synchronized and consistent from one device to another, thereby allowing equipment from different vendors to work seamlessly together. Bluetooth devices may be named according to a common naming concept. For example, a Bluetooth device may possess a Bluetooth Device Name (BDN) or a name associated with a unique Bluetooth Device Address (BDA). Bluetooth devices may also participate in an Internet Protocol (IP) network. If a Bluetooth device functions on an IP network, it may be provided with an IP address and an IP (network) name. Thus, a Bluetooth Device configured to participate on an IP network may contain, e.g., a BDN, a BDA, an IP address and an IP name. The term “IP name” refers to a name corresponding to an IP address of an interface.
An IEEE standard, IEEE 802.11, specifies technologies for wireless LANs and devices. Using 802.11, wireless networking may be accomplished with each single base station supporting several devices. In some examples, devices may come pre-equipped with wireless hardware or a user may install a separate piece of hardware, such as a card, that may include an antenna. By way of example, devices used in 802.11 typically include three notable elements, whether or not the device is an access point (AP), a mobile station (STA), a bridge, a PCMCIA card or another device: a radio transceiver; an antenna; and a MAC (Media Access Control) layer that controls packet flow between points in a network.
In addition, Multiple Interface Devices (MIDs) may be utilized in some wireless networks. MIDs may contain two independent network interfaces, such as a Bluetooth interface and an 802.11 interface, thus allowing the MID to participate on two separate networks as well as to interface with Bluetooth devices. The MID may have an IP address and a common IP (network) name associated with the IP address.
Wireless network devices may include, but are not limited to Bluetooth devices, Multiple Interface Devices (MIDs), 802.11x devices (IEEE 802.11 devices including, e.g., 802.11a, 802.11b and 802.11g devices), HomeRF (Home Radio Frequency) devices, Wi-Fi (Wireless Fidelity) devices, GPRS (General Packet Radio Service) devices, 3G cellular devices, 2.5G cellular devices, GSM (Global System for Mobile Communications) devices, EDGE (Enhanced Data for GSM Evolution) devices, TDMA type (Time Division Multiple Access) devices, or CDMA type (Code Division Multiple Access) devices, including CDMA2000. Each network device may contain addresses of varying types including but not limited to an IP address, a Bluetooth Device Address, a Bluetooth Common Name, a Bluetooth IP address, a Bluetooth IP Common Name, an 802.11 IP Address, an 802.11 IP common Name, or an IEEE MAC address.
Wireless networks can also involve methods and protocols found in, e.g., Mobile IP (Internet Protocol) systems, in PCS systems, and in other mobile network systems. With respect to Mobile IP, this involves a standard communications protocol created by the Internet Engineering Task Force (IETF). With Mobile IP, mobile device users can move across networks while maintaining their IP Address assigned once. See Request for Comments (RFC) 3344. NB: RFCs are formal documents of the Internet Engineering Task Force (IETF). Mobile IP enhances Internet Protocol (IP) and adds means to forward Internet traffic to mobile devices when connecting outside their home network. Mobile IP assigns each mobile node a home address on its home network and a care-of-address (CoA) that identifies the current location of the device within a network and its subnets. When a device is moved to a different network, it receives a new care-of address. A mobility agent on the home network can associate each home address with its care-of address. The mobile node can send the home agent a binding update each time it changes its care-of address using, e.g., Internet Control Message Protocol (ICMP).
In basic IP routing (e.g., outside mobile IP), routing mechanisms rely on the assumptions that each network node always has a constant attachment point to, e.g., the Internet and that each node's IP address identifies the network link it is attached to. In this document, the terminology “node” includes a connection point, which can include, e.g., a redistribution point or an end point for data transmissions, and which can recognize, process and/or forward communications to other nodes. For example, Internet routers can look at, e.g., an IP address prefix or the like identifying a device's network. Then, at a network level, routers can look at, e.g., a set of bits identifying a particular subnet. Then, at a subnet level, routers can look at, e.g., a set of bits identifying a particular device. With typical mobile IP communications, if a user disconnects a mobile device from, e.g., the Internet and tries to reconnect it at a new subnet, then the device has to be reconfigured with a new IP address, a proper netmask and a default router. Otherwise, routing protocols would not be able to deliver the packets properly.
Media Independent Handover Services:
In I.E.E.E. P802.21/D.01.09, September 2006, entitled Draft IEEE Standard for Local and Metropolitan Area Networks: Media Independent Handover Services, among other things, the document specifies 802 media access-independent mechanisms that optimize handovers between 802 systems and cellular systems. The I.E.E.E. 802.21 standard defines extensible media access independent mechanisms that enable the optimization of handovers between heterogeneous 802 systems and may facilitate handovers between 802 systems and cellular systems.
“The scope of the IEEE 802.21 (Media Independent Handover) standard is to develop a specification that provides link layer intelligence and other related network information to upper layers to optimize handovers between heterogeneous media. This includes links specified by 3GPP, 3GPP2 and both wired and wireless media in the IEEE 802 family of standards. Note, in this document, unless otherwise noted, “media” refers to method/mode of accessing a telecommunication system (e.g. cable, radio, satellite, etc.), as opposed to sensory aspects of communication (e.g. audio, video, etc.).” See 1.1 of I.E.E.E. P802.21/D.01.09, September 2006, entitled Draft IEEE Standard for Local and Metropolitan Area Networks: Media Independent Handover Services, the entire contents of which document is incorporated herein into and as part of this patent application. In addition, the provisional application from which priority is claimed herein also incorporated Draft 05 (Referred to herein as D05) of said standard, the entire contents of which is again incorporated herein by reference—i.e., see, e.g., I.E.E.E. P802.21/D05.00, April, 2007, Draft Standard for Local and Metropolitan Area Networks: Media Independent Handover Services, Sponsored by the LAN MAN Standards Committee of the I.E.E.E. Computer Society.
General Architecture:
Introduction:
The IEEE 802.21 standard is intended to facilitate a variety of handover methods. Such methods are generally classified as ‘hard’ or ‘soft’, depending on whether the handover procedure is “break before make” or “make before break” with respect to the data transport facilities that support the exchange of data packets between the mobile node and the network.
In general, handover involves cooperative use of both mobile node and network infrastructure in order to satisfy network operator and end user needs. Handover control, handover policies and other algorithms involved in handover decision making are generally handled by communication system elements which do not fall within the scope of the IEEE 802.21 standard. However, it is beneficial to describe certain aspects of the overall handover procedure so that the role and purpose of MIH Event Service, MIH Command Service, MIH Information Service and MIHF in overall handover process is clear.
General Design Principles:
The IEEE 802.21 standard is based on the following general design principles.
a) MIH Function is logical entity that helps and facilitates handover decision-making. Upper layers make handover decisions and link selection based on inputs and context from MIHF. Facilitating the recognition that a handover should take place is one of the key goals of MIHF. Discovery of information on how to make effective handover decisions is also a key component.
b) MIHF provides abstracted services to higher layers. From that perspective MIHF offers a unified interface to the upper layers. The service primitives exposed by this unified interface are based on the technology specific protocol entities of the different access networks. The MIHF communicates with the lower layers of the mobility-management protocol stack through technology-specific interfaces.
The specification of the MIHF interfaces with the lower layers generally does not fall within the scope of this standard. Such interfaces may already be specified as service access points (SAPs) within the standards that pertain to the respective access technologies, such as IEEE 802.1, IEEE 802.3, IEEE 802.11, IEEE 802.16, 3GPP and 3GPP2. This standard may contain recommendations to amend the existing access technology specific standards when modifications of the lower-layer interfaces may enable or enhance MIHF functionality.
c) Handover signaling (as part of handover execution and subsequent updates) may not be part of the standard. Different access networks support horizontal handover mechanisms (mobile initiated, network initiated, etc.). Handover initiation trigger may be useful in heterogeneous handovers when not done as per the homogeneous scheme.
d) MIHF may do further processing on MAC/PHY triggers and other related local events. Definition of this processing is outside the scope of the standard. The standard shall provide support for remote events as well. Events are advisory in nature. The decision whether to cause a handover or not based on these events is outside the scope of the standard.
e) The standard shall specify mechanisms to support MN-initiated, MN-controlled, network-initiated and network-controlled handovers.
f) The standard may support transparent inter-working with legacy equipment. Thus IEEE 802.21 compatible equipment should be able to co-exist with legacy non IEEE 802.21 compliant equipment.
Media Independent Handover Reference Framework:
The following sections describe aspects with regards to communication between different MIHF entities in the client device (MN) and the network.
MIHF functions communicate with each other for various purposes. The client device (mobile node) exchanges MIH information with its MIH Point of Service. The MIHF in any Network Entity becomes an MIH PoS when it communicates directly with a MN based MIHF. An MIH Network Entity may not have a direct connection to the MN and therefore does not constitute an MIH PoS for that particular MN. The same MIH Network Entity may still act as MIH PoS for a different MN. MIHF communication may not take place on all L2 interfaces of an MIH capable MN. As an example, on an MIH capable MN with three L2 interfaces namely 802.11, 802.16, and 802.3, the 802.3 interface may be used only for system administration and maintenance operations, while the 802.11 and 802.16 interfaces may engage in the provision of MIHF services. The MN may use L2 transport for exchanging MIH information with an MIH PoS that resides in the same Network Entity as its Network PoA. The MN may use L3 transport for exchanging MIH information with an MIH PoS that may not reside in the same Network Entity as its Network PoA. The framework supports use of either L2 or L3 mechanisms toward communication among MIH network entities.
FIG. 8 shows an MIH communication model. The model shows MIHFs in different distinctive roles and the communication relationships amongst them. The communication relationship shown in FIG. 8 applies only to MIHFs. It is noteworthy that each of the communication relationships in the communication model does not imply a particular transport mechanism. Rather, a communication relationship only intends to show that MIHF related information passing is possible between the two distinctive MIHFs. Moreover, 1) MIHF on the MN, 2) MIH PoS on the Network Entity that includes the serving PoA of the MN, 3) MIH PoS on the Network Entity that includes a candidate PoA for the MN (a candidate PoA is a PoA that the MN is aware of but not currently attached to; it becomes the target PoA if a handover eventually occurs), 4) MIH PoS on a Network Entity that does not include a PoA for the MN, 5) MIH non-PoS on a Network Entity that does not include a PoA for the MN.
The communication model also identifies the following communication reference points between different instances of MIHFs.
1) Communication reference point R1: Reference Point R1 refers to MIHF procedures between the MIHF on the MN and the MIH PoS on the Network Entity of its serving PoA. R1 may encompass communication interfaces over both L2 and L3 and above. MIHF content passed over R1 may be related to MIIS, MIES, or MICS.
2) Communication reference point R2: Reference Point R2 refers to MIHF procedures between the MIHF on the MN and the MIH PoS on the Network Entity of a candidate PoA. R2 may encompass communication interfaces over both L2 and L3 and above. MIHF content passed over R2 may be related to MIIS, MIES, or MICS.
3) Communication reference point R3: Reference Point R3 refers to MIHF procedures between the MIHF on the MN and the MIH PoS on a non-PoA Network Entity. R3 may encompass communication interfaces over L3 and above and possibly L2 transport protocol like Ethernet bridging, MPLS, etc. MIHF content passed over R3 may be related to MIIS, MIES, or MICS.
4) Communication reference point R4: Reference Point R4 refers to MIHF procedures between an MIH PoS in a Network Entity and an MIH non-PoS instance in another Network Entity. R4 may encompass communication interfaces over L3 and above. MIHF content passed over R4 may be related to MIIS, MIES, or MICS.
5) Communication reference point R5: Reference Point R5 refers to MIHF procedures between two MIH PoS instances in distinct Network Entities. R5 may encompass communication interfaces over L3 and above. MIHF content passed over R5 may be related to MIIS, MIES, or MICS.
Illustration of the MIH Communication Model:
A network model including MIH services is shown in FIG. 9 for greater illustration of the MIH Communication Reference Points. Moving from right to left, the model includes an MIH-capable mobile node (MN, far right) that supports multiple wired and wireless access technology options. The model assumes that the provisioning service provider either operates multiple access technologies or allows its user to roam into other networks when SLA in support of inter-working has been established. The MN has an MIHF implemented, which enables it to send specific MIH queries. The MN may have the information service partially implemented internally.
The model illustrates access networks that are connected in some loose, serial way to a core network (Operator 1-3 Core). Also depicted is an access network that is more tightly interworked or coupled (Access Network-3) The Operator 1-3 Core each might represent a service provider, corporate intranet provider or just another part of the visited or home access, or even core network. In this model the provisioning provider is operating Access Network-3 coupled via R1 to a core (labeled Visited/Home Core Network). The terms Visited and Home are used to indicate the provisioning service provider or enterprise. Any of the illustrated networks could be both a visited or home network depending on the relation of the operator to the provisioner of the MN. Network providers offer MIH services in their access networks (Access Network-1 to 4) to facilitate handover into their networks. Each access technology either advertises its MIH capability or responds to MIH service discovery. Each service provider for the access network allows access to one or more MIH Points of Service (PoS, compare with Communication Model) These PoS may provide some or all of the MIH services as determined during MIH capabilities discovery. The location or node of an MIH PoS is not fixed by the standard. The PoS location may vary based on operator deployment scenario and the technology-specific MIH architecture.
An MIH PoS may reside next to or be co-located with the point of attachment (PoA) in the access network Access Network 1, 2, 4 are typical). Alternatively the PoS may reside deeper inside the access or core networks (Access Network 3 is typical). As shown in FIG. 3, the MIH entity in the MN communicates with MIH network entities either by R1, R2 or R3 over any access network. When the PoA in the serving access network has a co-located MIH function, then an R1 reference connection terminates at the PoA which is also the PoS (MN to Access Network 1, 2, 4 of the model could all be R1) In that case an R3 reference connection would be terminated at any non-PoA (also illustrated by MN to Access Networks 1, 2, 4). MIH events may originate at both sides of an active R1 link. The MN is typically the first node to react to these events.
The interaction of visited and home network could be either for control and management purposes or for data transport purposes. It is also possible that due to roaming or SLA agreements, the home network may allow the MN to access the public Internet directly through a visited network. As illustrated, two MIH network entities may communicate with each other via R4 or R5 reference connections. The MIH capable PoA may also communicate with other MIH network entities via R3 and R4 reference points. The MIH capable MN could have a MIH communication with other PoA in the candidate access networks via R2 reference point to obtain information services about the candidate network.
With regard to the MIH Information Service (MIIS) the providers offer access to their information server located in a MIH PoS node (upper far left). The operator provides the MIIS to mobile nodes so they can obtain pertinent information including but not limited to new roaming lists, costs, provider identification information, provider services, priorities and any other information that would enable to select and utilize services. As illustrated, it is possible for the mobile node to be pre-provisioned with MIIS data by its provider.
Also possible is for the mobile node to obtain MIH information services from any access network of its provider. MIIS could also be available from another overlapping or nearby network, using that network's MIIS point of service. A provisioner's network (depicted here as coupled with Access Network 3) may utilize R3 and R4 interfaces to access other MIH entities like the provisioner's or visited network's MIH information server.
With regard to the MIH Command Service (MICS), any of the Information Database may be also used as command service PoS. The MN MIHF typically communicates with this server using a layer three transport.
MIHF Services:
The MIHF provides asynchronous and synchronous services through well defined SAPs for link layers and MIH users. In the case of a system with multiple network interfaces of arbitrary type, the upper layers may use the Event service, Command service and Information service provided by MIH to manage, determine, and control the state of the underlying interfaces.
These services provided by MIH help the upper layers in maintaining service continuity, service adaptation to varying quality of service, battery life conservation, and network discovery and link selection. In a system containing heterogeneous network interfaces of 802 types and cellular 3GPP, 3GPP2 types, the Media Independent Handover Function may help the upper layers to implement effective procedures to couple services across heterogeneous network interfaces. Upper layers may utilize services provided by the MIHF across different entities to query resources required for a handover operation between heterogeneous networks.
MIH services in mobile devices facilitate seamless handover between heterogeneous networks. An MIH user such as a mobility management protocol (example Mobile IP) could be supported for handover and seamless session continuity. This shall not preclude other protocols in addition to Mobile IP and even other upper layers from making use of MIH services to optimize handovers.
Mobile nodes employing MIH services would receive indications from link layers for asynchronous operations like Event service. The interaction with Command service and Information service will be through synchronous query and response type of mechanisms. The MIHF would also provide the functionality for the exchange of information between the network and host entities of the same media type. Note, if mechanism for such information exchange already exists with a given type of media (such as with some cellular media types), the MIHF will make use of the existing mechanism whenever possible.
MIH Protocol:
The IEEE 802.21 standard supports the Media Independent Event service, Media Independent Command service and Media Independent Information service. The MIH Protocol defines the format of the messages (i.e. MIHF packet with header and payload) that are exchanged between remote MIHF entities and the transport mechanisms that support the delivery of the messages. The selection of the transport mechanism is dependent on the access technology that connects the MN to the network and the location of the MIH PoS.
The packet payload for these services may be carried over L2 management frames, L2 data frames or other higher layer protocols. Wireless networks such as 802.11 and 802.16 have a management plane and support management frames which could be suitably enhanced for carrying the above payloads. However, the wired Ethernet network does not have management plane and may carry the above payloads only in data frames.
The IEEE 802.21 standard defines the packet format and payloads in media independent manner in standard TLV format. Thereafter, these packets may be encapsulated in a L2 MIH Protocol using MIHF ethertype when the payload needs to be sent over normal data frames as in case of Ethernet. In other cases the TLV based messages and payload may be directly encapsulated in media specific management frames. Alternatively, MIH protocol messages may be encapsulated using a lower layer (L2) or a higher layer (L3 and above) transport.
The IEEE 802.21 standard defines the format of MIH Protocol data unit (PDU) header and payload. Standard TLV format provides media-independent representation for the PDU payload contents. The MIHF PDUs are encapsulated in data frames with MIHF ethertype over 802 links. For 802.11 and 802.16 links extensions of media-specific management frames are recommended for carrying MIH messages. No assumptions are made in this standard regarding the transport of MIH messages over 3GPP and 3GPP2 access links at L2.
Media Independent Information Service:
Introduction:
Media Independent Information Service (MIIS) provides a framework by which an MIHF both in the mobile node and in the network may discover and obtain network information within a geographical area to facilitate handovers. The objective is to acquire a global view of all the heterogeneous networks relevant to the MN in the area to facilitate seamless handovers when roaming across these networks.
Media Independent Information Service includes support for various Information Elements (IEs). Information Elements provide information that is essential for a network selector to make intelligent handover decision.
Depending on the type of mobility, support for different types of information elements may be necessary for performing handovers. For example in case of horizontal handovers across different PoAs of the same access network, information available from lower link layers of access network may be sufficient. In such cases information elements like intra-technology neighbor reports and other link layer information required during handovers is directly available from the access network. In such cases the availability of higher layer services offered by the network may not change appreciably across different network point of attachment.
On the other hand, during vertical handovers there is a need to select appropriate PoA in the new network based on both optimum link layer connectivity as well as availability of appropriate higher layer services to permit service and session continuity for active user applications.
Media Independent Information Service (MIIS) provides the capability for obtaining the necessary information for handovers. This includes information about lower layers such as neighbor maps and other link layer parameters as well as information about available higher layer services such as internet connectivity, availability of VPN services, etc. The set of different higher layer services provided by the MIIS may constantly evolve. At the same time the list of access networks that are supported by MIIS may also evolve. As such, there is a need for flexibility and extensibility in the way the MIIS provides support for different information elements. Towards this end the MIIS defines a schema. The schema helps a client of MIIS to discover the capabilities of MIIS and also discover the entire set of different access networks and IEs supported by a particular implementation. Schema representation also allows the mobile node to query the information in a more flexible and efficient manner. As part of defining this schema the MIIS may also identify a set of basic information elements that may define the core functionality of different implementations of MIIS. Other information elements as they are added may become part of the extended set of MIIS capabilities.
MIIS provides information about different access networks such as 802 networks, 3GPP networks and 3GPP2 networks. The MIIS also allows this collective information to be accessed from any single network.
Thus for example using an 802.11 access network, it may be possible to get information not only about all other 802 networks in a particular region but also that of 3GPP and 3GPP2 networks as well. Similarly using a 3GPP2 interface, it may be possible to get access to information about all 802 and 3GPP networks in a given region. This capability allows the mobile node to use its currently active access network and scan for other available access networks in a geographical region. Thus, a mobile node is freed from the burden of powering up each of its individual radios and establishing network connectivity for the purpose of accessing heterogeneous network information. MIIS enables this functionality across all available access networks by providing uniform way to retrieve heterogeneous network information in any geographical area.
Information Service Elements:
The main goal behind the Information service is to allow mobile node and network entities to discover information that may influence the selection of appropriate networks during handovers. This information is intended to be primarily used by a policy engine entity that may make effective handover decisions based on this information. This information service is expected to provide mostly static type of information, although network configuration changes must also be accounted for. Other dynamic information about different access networks such as current available resource levels, state parameters, dynamic statistics etc. should be obtained directly from the respective access networks. Some of the key motivations behind the Information Service are as follows:
1) Provide information about the availability of access networks in a geographical area. Further, this information could be retrieved using any wireless network, for example, information about a nearby WiFi hotspot could be obtained using a GSM, CDMA, or any other cellular network, whether by means of request/response signaling, or information that is specifically or implicitly broadcast over those cellular networks. Alternatively, this information could be maintained in an internal database by the MN.
2) Provide static link layer information parameters that could help the mobile devices in selecting the appropriate access network. For example knowledge of whether security and QoS are supported on a particular access network may influence the decision to select such an access network during handovers.
3) The link layer information comprising of neighbor reports and information about capabilities of different PoAs could also aid in configuring the radios optimally (to the extent possible) for connecting to available/selected access networks. For example knowing about supported channels by different PoAs may help in configuring the channels optimally as opposed to scanning, beaconing etc. and then finding out this information. However, for most part, dynamic link layer parameters have to be obtained or selected based on direct interaction with the access networks and the Information Service may not be able to help much in that regard.
4) Provide an indication of higher layer services supported by different access networks and other relevant information that may aid in making handover decisions. Such information may not be available (or could not be made available) directly from MAC/PHY layers of specific access networks, but could be provided as part of the Information service. For example, in certain cases classification of different networks into categories such as public, enterprise, home, others, etc. may influence handover decision. Other information here may be more vendor/network specific in nature and could be specified in that form.
The information service elements are classified into three groups:
1) General Access Network Information: These information elements give a general overview of the different networks providing coverage within an area such as list of available networks and their associated operators, roaming agreements between different operators, cost of connecting to the network and network security and quality of service capabilities.
2) Information about Points of Attachment: These information elements provide information about different PoAs for each of the available access networks. These IEs include PoA addressing information, PoA location, data rates supported, the type of PHY and MAC layers and any channel parameters to optimize link layer connectivity. This may also include higher layer services and individual capabilities of different PoAs.
3) Other Information may be vendor/network specific, and could be specified appropriately.
Media Independent Handover Protocol:
Introduction:
The MIHF provides asynchronous and synchronous services through well defined SAPs for lower layers and upper layers. The services provided include the Event Service (ES), Command Service (CS), and Information Service (IS). Detailed description about MIH services are found in the 802.21 draft document. MIH SAPs include the MIH upper layer SAP, which is used by the users of MIH to gain access to various MIHF services, and MIH lower layer SAPs, which are used by MIHF to gain access and control of a variety of media dependent lower layer resources.
The MIH protocol defines frame formats for exchanging messages between peer MIHF entities. These messages are based on the primitives which are part of Media Independent Event service, Media Independent Command service and Media Independent Information service. IEEE 802.21 supports Media Independent Handover Function in mobile node, and network. The MIH Protocol allows peer MIHF entities to interact with each other.
In order for mobile node's MIHF entity to commence MIH protocol procedures, MIHF entity of mobile node may discover its peer remote MIHF entities. Peer remote MIHF entity is the correspondent MIHF entity with which MIHF of mobile node exchanges MIH protocol messages. Because peer remote MIHF entities reside in anywhere of the network, MIHF entity of mobile node may discover MIHF entity in the network before initiating MIH protocol procedure. This is done through the MIH Function Discovery procedure.
MIH Function Discovery can be done either at Layer 2 or Layer 3. However, this document only specifies how MIH Function Discovery is performed at Layer 2, when both MIH Functions are located within the same broadcast domain. MIH Function Discovery may be performed either through the MIH protocol (i.e. using L2 encapsulation such as LLC) or through media specific Layer 2 broadcast messages (i.e. 802.11 beacons, 802.16 DCD). MIH Function Discovery at Layer 3 is outside of scope of 802.21.
Once the peer MIHF has been discovered, the MN may discover the capabilities of the peer MIHF. This is done through the MIH Capability Discovery procedure. MIH Capability Discovery may be performed either through the MIH protocol or through media specific Layer 2 broadcast messages (i.e. 802.11 beacons, 802.16 DCD).
When the peer MIHF resides within the same broadcast domain as the MN, MIH Function Discovery can be performed using only MIH Capability Discovery.
Protocol Description:
The Media Independent Handover Protocol provides the following services:
1) MIHF Discovery (Layer 2 only): The MIHF in mobile node or in the network discovers which entity in the access networks supports MIHF.
2) MIH Capability Discovery: The MIHF entity discovers a list of supported events and commands, as well as supported query types for the Information Service.
3) MIH Remote Registration: Remote MIHF in different entities may register with each other to establish a new MIH session.
4) MIH Event Subscription: Interested entities may want to subscribe to a particular set of events from a given MIH-enabled entity.
5) MIH message exchange: Remote MIHF may exchange MIH messages using MIH payload and MIH protocol over a suitable transport. As part of message exchange the peer MIH Function entities may use the MIES, MICS and MIIS for effective handovers.
The standard describes the MIH frame format, message formats, and the procedures for MIH message exchange to facilitate handover in a media independent manner. However, handover policy and handover decision-making is outside the scope of the standard.
MIH Protocol Frame Format:
In MIH protocol messages, all TLV definitions are always aligned on an octet boundary and hence no padding is required. FIG. 11 shows the components of the MIH protocol frame.
Message Parameter TLV Encoding:
The TLV encoding shown in FIG. 12 is used for all parameters in an MIH protocol message. In this regard, the Type field shall be one octet2, and the Length shall be encoded with the rules described below (reproduced from sub-clause 6.5.6.2). Moreover, TLV Type values shall be unique within the MIH protocol. The TLV encoding starts at 1 and any subsequent values are assigned in ascending order.
With respect to sub-clause 6.5.6.2, MIIS defines two methods for representing Information Elements: binary representation and RDF representation (see W3C Recommendation, “Resource Description Framework (RDF)—Concepts and Abstract Syntax” and W3C Recommendation, “RDF/XML Syntax Specification”). MIIS also defines two query methods. For requests using the binary representation, the TLV query method defined. In the binary representation method, Information Elements are represented and encoded in Type-Length-Value form as shown in FIG. 10. In that regard, the Length field is interpreted as follows.
Case 1: If the number of octets occupied by the Value field is less than 128, the size of the Length field is always 1 octet and the MSB of the octet is set to the value ‘0’. The values of the other seven bits of this octet indicate the actual length of the Value field.
Case 2: If the number of octets occupied by the Value field is exactly 128, the size of the Length field is one octet. The MSB of the Length octet is set to the value ‘1’ and the other seven bits of this octet are all set to the value ‘0’.
Case 3: If the number of octets occupied by the Value field is greater than 128, then the Length field is always greater than 1 octet. The MSB of the first octet of the Length field is set to the value ‘1’ and the remaining 7 bits of the first octet indicate the number of octets that are appended further. The number represented by the 2nd and subsequent octets of the Length field, when added to 128, indicates the total size of the Value field, in octets.
Illustrative Architecture:
FIG. 13 depicts some illustrative architectural components that can be employed in some illustrative and non-limiting implementations including wireless access points to which client devices communicate. In this regard, FIG. 13 shows an illustrative wireline network 20 connected to a wireless local area network (WLAN) generally designated 21. The WLAN 21 includes an access point (AP) 22 and a number of user stations 23, 24. For example, the wireline network 20 can include the Internet or a corporate data processing network. For example, the access point 22 can be a wireless router, and the user stations 23, 24 can be, e.g., portable computers, personal desk-top computers, PDAs, portable voice-over-IP telephones and/or other devices. The access point 22 has a network interface 25 linked to the wireline network 21, and a wireless transceiver in communication with the user stations 23, 24. For example, the wireless transceiver 26 can include an antenna 27 for radio or microwave frequency communication with the user stations 23, 25. The access point 22 also has a processor 28, a program memory 29, and a random access memory 31. The user station 23 has a wireless transceiver 35 including an antenna 36 for communication with the access point station 22. In a similar fashion, the user station 24 has a wireless transceiver 38 and an antenna 39 for communication to the access point 22. By way of example, in some embodiments an authenticator could be employed within such an access point (AP) and/or a supplicant or peer could be employed within a mobile node or user station.
FIG. 14 shows an illustrative computer or control unit that can be used to implement computerized process steps, to be carried out by devices, such as, e.g., an access point, a user station, a source node or destination node in some embodiments. In some embodiments, the computer or control unit includes a central processing unit (CPU) 322, which can communicate with a set of input/output (I/O) device(s) 324 over a bus 326. The I/O devices 324 can include, for example, a keyboard, monitor, and/or other devices. The CPU 322 can communicate with a computer readable medium (e.g., conventional volatile or non-volatile data storage devices) 328 (hereafter “memory 328”) over the bus 326. The interaction between a CPU 322, I/O devices 324, a bus 326, and a memory 328 can be like that known in the art. Memory 328 can include, e.g., data 330. The memory 328 can also store software 338. The software 338 can include a number of modules 340 for implementing the steps of processes. Conventional programming techniques may be used to implement these modules. Memory 328 can also store the above and/or other data file(s). In some embodiments, the various methods described herein may be implemented via a computer program product for use with a computer system. This implementation may, for example, include a series of computer instructions fixed on a computer readable medium (e.g., a diskette, a CD-ROM, ROM or the like) or transmittable to a computer system via and interface device, such as a modem or the like. A communication medium may be substantially tangible (e.g., communication lines) and/or substantially intangible (e.g., wireless media using microwave, light, infrared, etc.). The computer instructions can be written in various programming languages and/or can be stored in memory device(s), such as semiconductor devices (e.g., chips or circuits), magnetic devices, optical devices and/or other memory devices. In the various embodiments, the transmission may use any appropriate communications technology.